The invention relates to a device which enables the driver of a motor vehicle to control sequentially a gearbox of the traditional type, that is, with hand-operated selection and engagement of gears. A gearbox of this type, hereinafter referred to as a gate change gearbox, is generally controlled by a selection lever which, through rotations and successive translations, is capable of selecting and engaging the required gear by shifting the corresponding gearwheels by means of a detent.
Devices for the sequential control of gate change gearboxes are disclosed, for example, in European patent application EP 0 616 153 and in international patent application WO 96/23995.
The above-mentioned European document discloses a control device which provides for the use of radial positive cams capable of engaging the gearwheels corresponding to the selected gear as a result of the rotation of a camshaft; a ratchet selector controls the stepwise rotation of the said camshaft towards a higher or lower gear in accordance with the command given by the operator through the gear selection lever. This solution has considerable mechanical complexity, involves the simultaneous use of all the cams and requires additional linkages to enable the cams to select and engage the desired gear.
The above-mentioned international patent application, on the other hand, discloses a device for controlling the two actuating levers of a traditional gate change gearbox in which the rods connected to these levers are set in motion by arms which are in turn connected to a rotating drum equipped with a pair of axial cams which engage pins provided on these arms. The stepwise rotation of the drum, which in this case also is brought about by means of a ratchet selector, enables each of the two cams constantly to control the position of one of the levers and hence the position of the group of gearwheels of the gearbox connected thereto. This solution also has the disadvantage of considerable mechanical complexity, since it involves the use of further mechanical members in addition to the existing controls. Moreover, it can be applied only to gearboxes operated by means of a double lever, unless a further mechanical unit is introduced to combine the movements of the various actuating members. Furthermore, the engine compartment of the vehicle is encumbered by the linkages and the housing of the drum, which has to be positioned outside of and separately from the gearbox.
It is the object of the present invention to provide an improved device for the sequential control of a gate change gearbox, which is structurally simple and easy to manufacture, which is of compact sizes, particularly in the axial direction, which consists of few components and which can be operated either in a completely automatic mode or with the possibility to shift between automatic and manual modes.
The invention solves the above technical problems by providing a device for the sequential control of gearboxes with hand-operated selection and engagement of gears for motor vehicles. Further advantageous characteristics are defined in the dependent claims. vehicles. Further advantageous characteristics are defined in the dependent claims.
As will be described in more detail below, a control device according to the present invention offers the following advantages: the space taken up in the engine compartment is reduced to a minimum; mechanical performance is optimised; the forks of the gearwheel groups of the gearbox can be actuated directly; operation can be readily automated.